Rectifier



Jan. 19, '1932. J, SLEPIAN 1,842,212

RECTIFIER Filed Sept. 13, 1928 INVENTOR J05 6 072 Sl'epz'an.

MW I

TTORNEY Patented Jan. 19, 1932 UNITED STATES PATENT oFFics v JOSEPH sum,01' PITTSBUMH, mns znvam ABSIGHOB '10 W'IIKGEQUSE ELECTRIC smother-nameOOIPANY, A. CORPORATION Oil PENNSYLVANIA.

'BICTII'IEB Application fled September 18, me. mm Ho. scam.

-My invention relates to rectifiers and par-v ticularl to rectifiers ofthe junction type which epend for operativeness 0n the unilateralelectrical conductivity by the layers i of solid materials.

One of the objects of my invention is to provide a junction rectifier inwhich the reverse currentis reduced to a minimum.

Another object ofmy inventioniis to pro vlde rectifiers of the junctiontype, of such form that the size and cost for a glven output capacityare minimized by reducing the heat dissipkated in the flow of reversecurrent.

0t or objects of my invention will be apparent on reading the followingspecification, talllrie'rlil, in connection with the rawing, in w c Thefigure is a sectional view of a rectifier embodying the principles of myinvention. 30 It is now well known that if. a block of copper has aportion of thesurface oxidized and contacts are made to the mothercopper and to the surface of the oxide respectively, a circuit elementis obtained which possesses a uni-lateral conductivity; that is to say,it conducts electricity much more readily in the direction in whichelectrons flow from the mother cop r into the oxide than in thedirection in w 00 into the mother copper. By properly combiningelementary units 0 the above described character, an arrangement whichwill I convert alternating current into direct current may be produced.Such arran description here.

It is found, however, that,while the current flow in the so-callednon-conductive direc- P tion may he made very small, it is notabsolutely zero." For most practical purposes, however, it is desirablethat this reverse current shall be made as small as awhile lnvestigationshows that the magnitude of the reverse current is lar ly determined hythe rimeter of the opening which must made is the oxide layer coverinthe surface of the copper in order to make e ectrical contact he- 1tween the mother copper and conductors of the circuit in which the unitis included.

m It is fuer found that with a ven per-- .as to have no shar edges orpoints;

ich electrons flow from the oxide 7 I mentsare too well known to the artto need etailed ture for imeter for the boundary of this 0 ning, thereverse current may be minimi if a margm 1s left between the terminalplates which are used to make contact with the outer surface of theoxide and the boundary edge between the oxide and the mother copper. Itis also found that reverse current is minimized if the oxidized surfaceis of such form In accordance with one feature of my invention, I makethe copper block in a form having no sharp ed or points; for instance,in the form 0 a circular rod or cylinder with rounded ends. Ithen makecontact between a line terminal and the mother metal underlying theoxide by piercing the oxide surface at one int with a hole only slightlylarger than t e line terminal to be engaged. By this means; theperimeter of the boundary edge of the layer between the mother metal andthe oxide is minimized, and reverse current is reduced by reason of theshortness of this boundary and of the absence of sharp edgesand pointson the oxidized surface. In general, 1t is desirable that the length ofthe perimeter of the junction of the la er of compound with the mothermetal shall e less than the square root of 1' times the area of thejunction,

where the perimeter and the area are exressed in corresponding units.

With the foregoing principles and ob ects in mind,my invention may beembodied m a structure such as that shown in the figure, m

which a copper cylinder 1 with rounded ends has its entire surfaceoxidized by heating in contact with oxygen to approximately 1000" C. Theunit is maintained at this temperaas about three minutes and is thencooled in the course of about five minutes to a temperature of 700 C. Itmay then be rapidly quenched by plunging 1t into water or anothersuitable cooling medium. Such me treatment covers the entire surface ofthe cyl- I v inder l with layer or layers 2 of oxidized cope be mafie tothe oxidized surface 2 by any suitable method, such as surrounding it bya sheath 5 of impressionable metal such as lead. Finely pounded graphitemay, if desired, be rubbed on the portion of the oxide surface whichunderlies the sheath 5. A split sleeve 6 of copper or other suitableconducting ma- ;terial may be placed around the layer 5 and boltedtightly into contact therewith by bolts extending through lugs 8. Aterminal 9 may be held tightly in contact with the sleeve the bolts 7.

unit made up in the manner described will be found to have asubstantially uni-directional conductivity and it will be found that theleakage current in the non-conductive direction will be very small. Amargin of separation is preferably left between the edge of the opening4 and the edge of the impressionable metal contact 6.

While I have described my invention as applied to junction rectifiersemploying oxidized copper, it will be obvious that it is not limited inuse to that material, but may be applied to other junction rectifierelements employing compounds of other metals; for instance, iron oxide.It will also be recognized that small perimeters of the edge of thelayer, margin of separation between the contact sheath and that edge,and absence of sharp corners are adjunctive features in the 1rinvention. Thus, in the embodiment of my invention shown in the drawing,it will be noted that the corners of the oxide layer or layers arerounded, as indicated at 30. p

1 Itwill be seenthat in accordance with my invention, I have providedjunction rectifiers of forms inwhich the reverse current is minimizedthereby reducing losses and increasing the current and voltage capacityof the result-' ing elements, since such capacity is largely determinedby ability to dissipate the heat generated by leakage current.

In accordance with the patent statutes. I have described severalembodiments of my invention; however, the rinciples thereof are capableof different em odiments which will be evident to those skilled in theart. I accordingly desire that the following claims shall be limitedonly in accordance with the expressterms and with the limitationsimposed by the prior art.

I claim as my invention: 1. A solid rectifier of the junction type whichdepends for operativeness upon t e unilateral electrical conductivityacross layers of solid materials, characterized by having a base ofmother metal, a layer of a compound of said metal covering substantiallythe entire surface thereof, and an electrical connection to said mothermetal through an opening in said compound relatively small compared tothe surface thereof.

2. A rectifier comprising a base of mother copper, an oxidized layercovering substantially the entire surface of said copper and aconnection to the mother copper through an openin in said layerrelatively small compared to t e entire surface thereof.

3. A solid rectifier of the junction type which depends foroperativeness upon t e unilateral electrical conductivity across layersof solid materials, characterized b having a base of mother metal, a'laer 0 a compound of said metal forme thereon and covering substantiallythe entire surface thereof and a single opening in said layer relativelysmall compared to the entire surface thereof.

4. A rectifier comprising a base of mother metal, a layer of a compoundof said metal covering substantially the entire surface thereof, asingle opening in said layer having an area small compared to the entiresurface thereof, and line terminal means adapted to make contact withsaid mother metal through said opening and filling nearly the entirecross section thereof.

5. A rectifier comprising a base of mother metal and having a layer of acompound thereof partially covering its surface, of such shape that thelength of the perimeter of the junction of the layer of compound withthe mother metal is less than the square root of perimeter and area areexpressed in corresponding units.

6. A solid rectifier of the junction type which depends foroperativeness upon t e unilateral electrical conductivity across layersof solid materials, characterized by having such .a unilaterallconducting surface between two layers 0 dissimilar solids in contactwith each other, one of said solids being a compound havin lessconductivit than the other of saidsohds, said compoun coveringsubstantially the entire surface of said other solid, said compoundhavin a single opening therein relatively smal compared to the entireextent thereof, and a terminal connector which is of a cross-sectionsmaller than said openin and which makes electrical contact with sa1dother solid.

7 A solid rectifier of the junction type which depends for operativenessupon t e unilateral electrical conductivity across layers of solidmaterials, characterized by having a rod of mother metal having arounded cross-sectional shape, a layer of a compound 2 times the area ofthe junction, where the of said. metal formed thereon and coverinsubstantially the entire surface thereof, sai

v compound In testimony whereof, I have hereunto suhscribed my name this6th day of September, 192%.

rese'rn SLEPIAN.

